1. Technical Field
The present invention relates to an ink composition having excellent reproduction of black and an ink jet recording method using the same.
2. Background Art
An ink composition for ink jet recording is required to have the following properties.
(1) Good print and image quality can be realized on various recording media, especially plain paper.
(2) The drying rate of the ink after printing is high enough to cause no smear even when the print is rubbed immediately after printing.
(3) Ink droplets can be stably ejected through nozzles of a printing head nozzle without causing unfavorable phenomena such as clogging, dropout, and without ejecting ink droplets with trajectories non-perpendicular to the printing head.
(4) The resultant print has water resistance high enough to cause, upon contact with water, neither defacement of the print nor washing away of the print.
(5) The storage stability of the ink composition is enough not to cause any change in properties even when the ink composition is stored for a long period of time.
(6) The ink composition does not attack printer members which come into contact with the ink composition.
In particular, a black ink composition is important for ink jet recording in both monochrome printing and full-color printing and, thus, should satisfy the above property requirements.
Various black ink compositions have been proposed with a view to satisfying the above property requirements.
For example, C.I. Food Black 2 (Japanese Patent Laid-Open Publication No. 93766/1984) and dyes having structures similar thereto (Japanese Patent Laid-Open Publication No. 91577/1991) have been used widely as a dye for a black ink in the art. Further, an attempt was made to use a particular ink composition to improve properties such as lightfastness (Japanese Patent Laid-Open Publication No. 36279/1990). Furthermore, several proposals have been made to improve the water resistance of the print (for example, Japanese Patent Laid-Open Publication Nos. 91577/1991, 226175/1992, and 233975/1992).
Furthermore, U.S. Patent Nos. 4,963,189 and 5,203,912 describe dyes. (Some of the dyes are covered by the formula (I) described below.) The dyes described in the U.S. patents can be easily dissolved in basic water but are insoluble in neutral water. These patents describe that, by taking advantage of this property, the ink composition containing the dyes can improve the water resistance of the print.
The conventional ink compositions, however, have room for improvement, and a need still exists for an ink composition capable of satisfying the property requirements (1) to (6).